The present invention relates to a combustor of a high pressure burner for a regenerative cooling type rocket engine and a method of fabrication thereof.
A conventional combustor of a high pressure burner for a regenerative cooling tuype rocket engine comprises an inner tube 2 with a throat 3 as shown in FIGS. 7 and 8. A plurality of projections 2' radially extend from the outer periphery of the inner tube 2 to define regenerative coolant grooves 4. Because of the throat 3 which is reduced in diameter, two-piece divided semicylindrical outer tubes 1a and 1b are fitted over the inner tube 2 and joined therewith through the projections 2' so as to support pressure in the grooves 4 and combustion pressure by the outer tubes 1a and 1b.
The conventional combustor of the type described above is fabricated by electroforming, powder infiltration, hydrostatic forming (CIP method), diffused junction or the like.
In fabrication of a combustor by electroforming, regenerative coolant grooves 4 are machined at the outer periphery of the inner tube 2 made of a Cu alloy. Cu is electroformed through an intermediate plated layer a made of Cu, Ag, Mo, Au or the like over the outer periphery of the inner tube 2, whereby the outer tube 1 is defined. The combustor thus fabricated is subjected to various kinds of tests.
In fabrication of the combustor by powder infiltration, as shown in FIGS. 10 and 11 illustrating copper powder infiltration, a copper inner tube 1 is formed at its outer periphery with the regenerative coolant grooves 4 into which water-soluble core b is filled. Two-piece divided semicylindrical stainless-steel outer tubes 1a and 1b are fitted over the inner tube 2 through a copper powder layer c and the whole structure is heated to melt the copper powder layer so as to join the outer tubes 1a and 1b with the inner tube 2. Thereafter, the two-piece divided semicylindrical outer tubes 1a and 1b are securely joined together. The combustor thus fabricated is subjected to various kinds of tests.
In fabrication of a combustor by hydrostatic forming (CIP method), as shown in FIGS. 12 and 13, an alloy d having a low melting point is filled into each of the regenerative coolant grooves 4 on the inner tube 2 and a rubber mold e is fitted over the tube 2. Thereafter copper powder f is filled into a space defined between the mold e and the inner tube 2. After the completion of the hydrostatic forming, the low-melting point alloy d is removed and then sintering is carried out, thereby forming a copper sintered tube g. Next two-piece divided semicylindrical outer tubes 1a and 1b are fitted over the tube g and are joined together by welding or the like. The combustor thus fabricated is subjected to various kinds of tests.
In fabrication of a combustor by diffused junction, as shown in FIGS. 14 and 15, the two-piece divided outer tubes 1a and 1b are fitted over the inner tube 2 with the regenerative coolant grooves 4 machined thereon and then the inner and outer tubes are tightened by jigs disposed on the sides of the inner and outer tubes, respectively. Argon gas is introduced into the combustor and the coolant grooves and the whole structure is heated in a hearth-treatment furnace so that due to force produced by the difference in thermal expansion between the inner and outer jigs and pressure of the argon gas, the inner tube 2 and the outer tubes 1a and 1b are deformed and rigidly joined together. That is, due to mutual diffusion of metal atoms in the vicinity of the abutments, the inner tube 2 and the outer tubes 1a and 1b are integrally joined together. Thereafter, a joint band 5 is fitted around the junction between the outer tubes 1a and 1b and then is welded to them.
In any of the conventional combustors except those fabricated by electroforming, due to the fact that the inner tube 2 is a unitary structure and has a throat 3 which is reduced in diameter, the two-piece divided outer tubes 1a and 1b are fited over the inner tube 2 and are welded together. As a result, the outer tube means which is to be one of the most important element for strength resistance of the combustor may be structurally problematic in assured strength and reliable quality. Furthermore, in the combustors fabricated by powder infiltration, hydrostatic forming and diffused junction except those fabricated by electroforming, due to the fact that two-piece divided outer tubes 1a and 1b are fitted over the inner tube 2 and joined together by welding or the like, fabrication steps are increased in number, resulting in increase in cost and fabrication period. In the combustor made by electroforming, there exists problems that a long fabrication period is required and that control in thickness of plated layer is extremely difficult.
In view of the above, a primary object of the present invention is to provide a combustor of a high pressure burner for a rocket engine an outer tube of which is fabricated as a unitary structure for stabilized and assured strength and for fabrication at low costs within a short time interval.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of some preferred embodiments thereof taken in conjunction with the accompanying drawings.